Production motor cars are required to pass various safety tests to ensure that they are sufficiently safe for use on public roads. It is desirable that the occupants of a motor car do not suffer injury when the motor car is in a collision. Therefore, at least one of the tests a motor car type has to pass is to ensure that a motor vehicle occupant will not suffer an acceleration higher than a certain amount during a collision. One of the safety tests carried out for vehicles is the United States of America Federal front impact test when the motor car is projected forwards at a speed of 35 miles per hour (15.65 meters per second) into a substantially solid immovable flat wall arranged perpendicular to the direction of motion of the motor car. This test therefore simulates what may happen if a motor car is accidentally driven directly into a solid and substantially immovable object such as a reinforced concrete bridge support at the side of the road or a very heavy vehicle.
FIG. 1 shows part-schematically a known motor vehicle type undergoing the United States of America Federal front impact test. As shown, the motor car 10 has four wheels 12 and is projected into the flat front, wall 14 of a substantially rigid immovable object 16. During the collision, a front crash load absorption structure 18 deforms as shown in FIGS. 2A to 2D. The front crash load absorption structure 18 has on each side of the car a primary crush can 20, a secondary crush can 22 and a tertiary crush can 24. The primary, secondary and tertiary crush cans 20, 22, 24 are permanently deformably crushable. The primary crush can 20 and secondary crush can 22 are joined together by an interface casting 26 and the secondary crush can 22 and tertiary crush can 24 are joined together by an upper wishbone casting 28 onto which an upper wishbone 30 of the front suspension is mounted. The tertiary crush can 24 is connected by a rear interface casting 32 to a front structure mounting member 34 of the body structure of the motor car 10.
As shown by the sequence of views from FIG. 2A to 2D, the crush cans 20, 22, 24, and also parts 186 and 96 are engineered to provide increasing crush strength from front to rear. Can 24, brackets 186 and underfloor longitudinal member 96 initiate at sufficiently high load to allow suitable crush of 20 and 22. Accordingly, during the collision, the primary crush cans 20 are first longitudinally crushed from the pre-collision configuration of FIG. 2A to the configuration of FIG. 2B in which the primary crush cans 20 are crushed, but the secondary 22 and tertiary 24 crush cans are still substantially undeformed. As the collision continues to the configuration of FIG. 2C, the secondary crush cans 22 are then crushed with the tertiary crush can 24 remaining substantially undeformed. As the collision continues to the configuration of FIG. 2D, the tertiary crush cans 24 and the underfloor 96 and brackets 186 are next at least partially crushed. After the collision, the primary, secondary and tertiary crush cans 20, 22 24 remain in substantially the crushed configuration shown in FIG. 2D. This sequential crush system has been considered highly advantageous since, dependent upon the extent of the collision, parts further back in the vehicle may not be damaged and may not need replacing and the cost of repairing relatively minor collisions can be minimised. Also, the sequential crush system is relatively predictable and parts of the vehicle further towards the rear where the occupants are located are not easily deformed such that the occupants 36, 38 are maintained safely in their occupant space 48 with only a negligible deformation of this space in relatively minor collisions.
The motor car 10 shown in FIG. 1 and FIGS. 2A to 2D has performed very well in front impact tests and it is noted that this vehicle has a 4.7 litre V8 engine 40 which has a relatively short block 42 leaving a sizable gap 44 longitudinally between the engine block 42 and structural cross-members 46 joining the two sides of the front crash load absorption structure 18 in the region of the interface castings 26.
However, in certain cases, it may be desirable from a product definition point of view to use an engine with a longer block whereby it may be more difficult to achieve good low acceleration of the occupants 36, 38, especially the driver who has a more confined space due to the steering wheel and a smaller main front airbag than the front passenger during frontal impacts.
The present invention aims to alleviate at least to a certain extent the problems and/or address at least to a certain extent the difficulties of the prior art.